Physical activity has numerous health benefits including a reduction in risk of colon and breast cancer. Physical activity may also alter the risk of endometrial cancer and epithelial ovarian cancer. Few studies have examined these potential relationships. Most prior studies have been case-control studies or record linkage studies that have used surrogate measures of activity. We propose to utilize data collected as part of the California Teachers Study (CTS), a cohort study of 133,479 female teachers and school administrators that was initiated in 1995, to address whether 1. Women who engage in moderate and strenuous physical activity for 4 or more hours per week on average, have a reduced risk of endometrial cancer and of ovarian cancer; 2. Strenuous physical activity provides greater protection against endometrial cancer and ovarian cancer than does moderate physical activity. Additionally we propose to analyze data collected from a group of population-based control subjects to compare their responses to the self-completed, mailed CTS questionnaire on physical activity to their responses to an in-depth, in-person interview that collected lifetime history of physical activity to determine whether the two types of questionnaires measure the same or different aspects of physical activity and to determine whether demographic or other factors affect the comparability of information derived from the two questionnaire approaches.